Saw this only one year before it was washed away by the flood of 2013.  Called Mosquitofern because it was hoped that it would choke the surface of ponds and prevent the larva or mosquitoes from breathing.  Good luck.Mosquitofern ( Azolla neomexicana)

Mosquitofern ( Azolla neomexicana)

From a distance it can be mistaken for duckweed, which is the yellow-green floating plant at the bottom of the picture.Mosquitofern ( Azolla neomexicana)

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